MODELING OF NONPOINT SOURCE POLLUTION OF NITROGEN AT THE WATERSHED SCALE¹

Abstract

The Watershed Nutrient Transport and Transformation (NTT‐Watershed) model is a physically based, energy‐driven, multiple land use, distributed model that is capable of simulating water and nutrient transport in a watershed. The topographic features and subsurface properties of the watershed are refined into uniform, homogeneous square grids. The vertical discretization includes vegetation, overland flow, soil water redistribution and groundwater zones. The chemical submodel simulates the nitrogen dynamics in terrestrial and aquatic systems. Three chemical state variables are considered (NO3‐‐, NH4+, and Org‐N). The NTT‐Watershed model was used to simulate the fate and transport of nitrogen in the Muddy Brook watershed in Connecticut. The model was shown to be capable of capturing the hydrologic and portions of the nitrogen dynamics in the watershed. Watershed planners could use this model in developing strategies of best management practices that could result in maximizing the reductions of nitrogen export from a watershed.

HYDROLOGIC MODELING AT THE WATERSHED SCALE USING NPSM1

“…Currently, due to point source treatment improvements and increases in agricultural and urban land, nonpoint sources account for the majority of water quality problems (Rains and Latham, 1993;Chew et al, 1991). Nonpoint source pollutants come from urban runoff, agricultural and silvicultural runoff, erosion, and polluted groundwater discharges to surface waters (Heng and Nikolaidis, 1998). The growth of urban and agricultural areas and the resultant loading of nonpoint source pollutants, such as sediment and pesticides, to surface waters threatens aquatic ecosystems and drinking water supplies.…”

“…One drawback to the use of lumped parameter models is that the linear nature of these models prevents accurate description of the variable nature of nonpoint source pollutant transport due to variances in landscape-level characteristics (Greene and Cruise, 1996). In addition, the conceptually, rather than physically, based nature of these models makes intensive, site-specific calibration necessary such that the results are not transferable to other watersheds (Heng and Nikolaidis, 1998). Whittemore and Beebe (2000) characterize HSPF as having parameters with vague meanings, which makes it difficult to understand and communicate the link between changes in hydrology and water quality due to management actions.…”

A Spatially Distributed, Physically-Based Modeling Approach for Estimating Agricultural Nitrate Leaching to Groundwater

“…and NTT-Watershed, Heng and Nikolaidis 1998 [33]) solve the Richards' equation for soil water dynamics in the unsaturated zone.…”

A decision support system for planning and management of sustainable livestock production in the Midwest

“…These models provide the analytical tool for quantifying the effects of both point and non-point source pollution on water quality (NIX, 1994; Presti and Lubello, 1993;Donigian and Huber, 1991). In addition, the result from these models can assess potential consequences of alternative management scenario or policy-level decisions; and can also be a cost-effective and efficient substitute to longterm monitoring of fields, watersheds, and basins (Heng and Nlkolaidus, 1998).…”